A potential long term solution to type I diabetes is the transplantation of the islets of Langerhans. Notable success in recent clinical trials has been achieved with large numbers of human islets used for transplantation combined with highly developed immunosuppressive treatment protocols. The results show how effective treatment can be for a few patients but there are nowhere near adequate numbers of human islets available from donors to meet the needs of the human population. The best candidate non-human donor for islets is the pig. For islet transplantation to be optimal it is likely that improvements in their survival must be made by increasing the blood supply to the transplanted islet. Endothelial cells (EC) have been utilized to form a de novo microvascular bed in three-dimensional collagen gels. We have shown that overexpression of Bcl-2 enhances revascularization and protects human EC from destruction by cytotoxic lymphocytes. Conditions will be developed to create revascularized porcine islets or "microorgans" in these collagen gels to promote islet survival and function in vivo. Human endothelial cells and islets will be combined and their structure/function properties characterized. We will test the functionality of these grafts by performing glucose tolerance tests and insulin secretion over time. We will determine the optimum combination of human microvessels with pig islets. Proof of principle experiments will be done to show that these microorgans can cure chemically induced diabetes. It might be clinically desirable to utilize syngeneic EC from an islet microorgan recipient for the formation of microvessels. Therefore we will attempt to culture sufficient EC derived from CD34+ progenitor cells to form the microorgans. Finally, we will evaluate the immunogenicity of the microorgan grafts by reconstitution of the human immune system in immunodeficient mouse models. These studies could lead to new methodologies to treat type I diabetes enhancing both the efficiency of islet transplantation and address the severe lack of donor islets. [unreadable] [unreadable] [unreadable]